Liquid treatment apparatus and method

ABSTRACT

Disclosed is a liquid treatment apparatus for processing a lower surface of the substrate. The apparatus includes a first nozzle disposed below a lower surface of the substrate retained by the substrate retaining unit to eject a treatment liquid towards the lower surface of the substrate, the first nozzle having a plurality of first ejection ports, which are arrayed from a position opposing a central portion of the substrate retained by the substrate retaining unit to a position opposing a peripheral portion of the substrate retained by the substrate retaining unit. An ejecting direction of the treatment liquid ejected from the first ejection port is inclined towards a rotation direction of the substrate rotated by the rotational driving unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priorities fromboth Japanese Patent Application No. 2010-293775 filed on Dec. 28, 2010,and Japanese Patent Application No. 2011-240325 filed on Nov. 1, 2011,the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a liquid treatment apparatus and aliquid treatment method used to conduct liquid treatment such ascleaning and etching for substrates by supplying a treatment liquid to alower surface of the substrate while spinning it.

BACKGROUND ART

There have been known conventional substrate cleaning apparatuses thatclean substrates such as semiconductor wafers (hereinafter, alsoreferred to simply as “wafer(s)”) by supplying a cleaning liquid to asubstrate which is rotating and held in horizontal posture.

JP9-290197A describes a substrate processing apparatus that includes aspin chuck for retaining a wafer in horizontal posture and rotating thewafer; and a cleaning liquid supply pipe extending inside a rotatingshaft of the spin chuck and having an opening for ejecting cleaningliquid towards the center of the lower surface of the wafer retained bythe spin chuck. The peripheral area of the wafer lower surface may notbe sufficiently cleaned if the cleaning liquid is ejected towards thecenter of the lower surface of the wafer W.

JP2005-353739A describes a substrate processing apparatus that includesa spin chuck for retaining the wafer in horizontal posture and rotatingthe wafer; and a two-fluid nozzle for jetting a two-fluid spray towardsthe upper surface of the wafer retained by the spin chuck. The two-fluidspray is formed from a nitrogen gas and a treatment liquid such as achemical liquid and is jetted in a band-like form having a length nearlyequivalent to the radius of the wafer. JP2005-353739A suggests that sucha two-fluid nozzle may also be disposed below the lower surface of thewafer to clean the lower surface. However, a specific configuration ofsuch an arrangement is not disclosed.

JP2008-130763A describes a substrate processing apparatus that includesa spin chuck for retaining the wafer in horizontal posture and rotatingthe wafer; a two-fluid nozzle for jetting a two fluid spray towards theupper surface of the wafer retained by the spin chuck, the two fluidspray being a mixture of a nitrogen gas and a treatment liquid such as achemical liquid and is jetted in a band-like form having a length nearlyequivalent to a diameter of the wafer; and another nozzle for ejecting atreatment fluid such as deionized water (DIW) towards the centralportion of the upper surface of the wafer W. In the apparatus ofJP2008-130763A, when a two-fluid nozzle jets a two fluid-spray onto theupper surface of a wafer W, the two-fluid nozzle scans the upper surfaceof the wafer W which is not rotating. Cleaning of the lower surface ofthe wafer W is not described in JP2008-130763A.

DISCLOSURE SUMMARY

The present disclosure provides a liquid treatment apparatus and aliquid treatment method capable of treating the lower surface of asubstrate efficiently.

In one aspect, there is provided a liquid treatment apparatus, whichincludes: a substrate retaining unit comprising a retaining memberconfigured to hold a peripheral edge of a substrate to retain thesubstrate horizontally; a rotational driving unit configured to rotatethe substrate retaining unit; a first nozzle disposed below a lowersurface of the substrate retained by the substrate retaining unit toeject a treatment liquid towards the lower surface of the substrate, thefirst nozzle comprising a plurality of first ejection ports, which arearrayed from a position opposing a central portion of the substrateretained by the substrate retaining unit to a position opposing aperipheral portion of the substrate retained by the substrate retainingunit; and a liquid supply mechanism that supplies a treatment liquid tothe first ejection ports, wherein each of the first ejection ports isconfigured to eject the treatment liquid towards the lower surface ofthe substrate in an ejecting direction which is inclined towards arotation direction of the substrate rotated by the rotational drivingunit.

In another aspect, there is provided a liquid treatment method, whichincludes: retaining a substrate in a horizontal posture; providing afirst nozzle comprising a plurality of first ejection ports below alower surface of the substrate retained by the substrate retaining unitsuch that the first ejection ports are arrayed from a position opposinga central portion of the substrate to a position opposing a peripheralportion of the substrate; rotating the substrate; and ejecting atreatment liquid from the first ejection ports toward a lower surface ofthe substrate in ejecting directions each having a component in arotation direction of the substrate.

In the foregoing aspects, due to the provision of the first ejectionports which are arrayed from a position opposing a central portion ofthe substrate to a position opposing a peripheral portion of thesubstrate, a treatment liquid can be supplied to the lower surface ofthe substrate with high uniformity. In addition, since the ejectingdirection of the treatment liquid ejected from the first ejection porttowards the lower surface of the substrate is inclined towards arotation direction of the substrate, bouncing (splash-back) of thetreatment liquid upon collision against the lower surface of the wafer Wcan be suppressed, resulting in Improved efficiency of the treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a liquid treatment system which includessubstrate cleaning apparatuses in one embodiment;

FIG. 2A is a vertical cross sectional view showing the configuration ofthe substrate cleaning apparatus in a state where a lift pin plate and acleaning liquid supply pipe are located at their lowered positions;

FIG. 2B is a vertical cross sectional view showing the configuration ofthe substrate cleaning apparatus in a state where the lift pin plate andthe cleaning liquid supply pipe are located at their raised positions;

FIG. 2C is a top plan view of the substrate cleaning apparatus in astate where a wafer is retained by a substrate retaining member andfixed retaining members as shown in FIG. 2A;

FIG. 3 is a perspective view showing the configuration of the lift pinplate of the substrate cleaning apparatus shown in FIGS. 2A and 2B;

FIG. 4 is a perspective view showing the configuration of a retainingplate of the substrate cleaning apparatus shown in FIGS. 2A and 2B;

FIG. 5 is an enlarged vertical cross sectional view showing theconfiguration of a connecting member extending downward from the liftpin plate and a hollow accommodation member extending downward from theretaining plate and accommodating the connecting member in the substratecleaning apparatus shown in FIGS. 2A and 2B;

FIG. 6 is an enlarged vertical cross sectional view showing theconfiguration of the substrate retaining member provided on theretaining plate in the substrate cleaning apparatus shown in FIGS. 2Aand 2B;

FIG. 7 is an enlarged vertical cross sectional view showing a statewhere the lift pin plate has been moved downward from the state shown inFIG. 6;

FIG. 8 is an enlarged vertical cross sectional view showing a statewhere the lift pin plate has been moved further downward from the stateshown in FIG. 7;

FIG. 9 is a perspective view showing the configuration of a treatmentfluid supply pipe and bar-shaped nozzle in the substrate cleaningapparatus shown in FIGS. 2A and 2B, and the configuration of a liftingmechanism for vertically moving them;

FIG. 10 is for explanation of the configuration of the treatment fluidsupply pipe and the bar-shaped nozzle, wherein (a) is a top plan view,(b) is a vertical cross sectional view taken along line Xb-Xb of (a),and (c) is a vertical cross sectional view taken along line Xc-Xc of(a);

FIG. 11 is for explanation of the status where only a liquid is ejectedfrom the bar-shaped nozzle, wherein (a) is a diagram showing regionswetted with the liquid upon reaching the lower surface of the wafer W,(b) shows a side view showing the manner of liquid ejection from anejecting port of a bar-shaped portion of the bar-shaped nozzle, and (c)is a side view showing the manner of liquid injection from an ejectionport of a central portion of the bar-shaped nozzle;

FIG. 12 is a diagram for explanation of spots formed on the wafer by thechemical liquid ejected from ejection ports of the bar-shaped nozzle;

FIG. 13 is for explanation for the status where a two-fluid spray isejected from the bar shaped nozzle, wherein (a) is a vertical crosssectional view of the bar-shaped portion of the bar-shaped nozzle, and(b) is a vertical cross sectional view of the central portion of thebar-shaped nozzle;

FIG. 14 shows diagrams showing variations of the manner in which aliquid-ejecting passage and a gas-ejecting passage meet near theejection port of the bar-shaped portion of the bar-shaped nozzle;

FIG. 15 is a schematic diagram for explaining a possible modification ofthe liquid treatment apparatus;

FIG. 16 shows schematic plan views showing modifications of arrangementof ejection ports in the bar-shaped nozzle;

FIG. 17 shows schematic plan views illustrating an example of a way ofshifting the bar-shaped nozzle while ejecting a liquid from the ejectionports; and

FIG. 18 shows a vertical cross sectional view and a schematic diagramshowing the configuration around the ejection port in a modifiedbar-shaped nozzle.

DESCRIPTION OF EMBODIMENTS

An embodiment of a liquid treatment apparatus will be described withreference to the accompanying drawings.

First, a liquid treatment system including a substrate cleaningapparatus in one embodiment of a liquid treatment apparatus will bedescribed below with reference to FIG. 1. As shown in FIG. 1, the liquidtreatment system includes: mounting tables 101 each for mounting thereona carrier accommodating a semiconductor wafer W (i.e., substrate to beprocessed) (hereinafter, simply referred to as “wafer W”) which istransported thereto from the outside of the system; a transport arm 102for removing the wafer W from the carrier; a shelf unit 103 for placingthereon the wafer W removed from the carrier by the transport arm 102;and a transport arm 104 for receiving the wafer W from the shelf unit103 and for transporting the wafer W to the substrate cleaning apparatus10. As shown in FIG. 1, a plurality of (twelve, in the embodiment ofFIG. 1) substrate cleaning apparatuses are installed in the liquidtreatment system.

Next, a schematic configuration of the substrate cleaning apparatus 10is described below with reference to FIGS. 2A and 2B. The substratecleaning apparatus 1.0 includes: a retaining plate 30 retaining thewafer W; a lift pin plate 20 provided above the retaining plate 30 andincluding lift pins 22 to support thereon the wafer W from below; arotational driving unit 39 equipped with an electric motor or the liketo rotate the retaining plate 30; a treatment fluid supply pipe 40routed through a through-hole 30 a formed centrally in the retainingplate 30 and a through-hole 20 a formed centrally in the lift pin plate20; and a bar-shaped nozzle 60 for ejecting treatment fluids suppliedvia the treatment fluid supply pipe 40 towards the lower surface of thewafer W. The lift pin plate 20 is configured to rotate with beinginterlocked with the retaining plate 30.

The lift pin plate 20, the treatment fluid supply pipe 40, and thebar-shaped nozzle 60 can be moved vertically relative to the retainingplate 30. FIG. 2A shows a state where the lift pin plate 20, thetreatment fluid supply pipe 40, and the bar-shaped nozzle 60 arepositioned at their respective lowered positions. FIG. 2B shows a statewhere the lift pin plate 20, the treatment fluid supply pipe 40, and thebar-shaped nozzle 60 are positioned at their respective raisedpositions. The lift pin plate 20, the treatment fluid supply pipe 40,and the bar-shaped nozzle 60 can be moved up and down between thelowered positions as shown in FIG. 2A and the raised positions as shownin FIG. 2B.

Next, constituent elements of the substrate cleaning apparatus aredescribed in detail below.

As shown in FIG. 3, the lift pin plate 20 has a disk-like shape with thethrough-hole 20 a formed in its central portion. An annular protrusion20 b is provided around the through-hole 20 a to prevent a liquid on thelift pin plate 20 from entering the through-hole 20 a. The treatmentfluid supply pipe 40 is routed through the through-hole 20 a. Aplurality of (three or four) lift pins 22 are provided on the uppersurface of the lift pin plate 20. The lift pins 22 are arranged at equalangular intervals on a circumference near the peripheral edge of thelift pin plate 20. Three rod-like connecting members 24 extend downwardfrom the lower surface (i.e., the surface opposite to the surfaceprovided with the lift pins 22) of the lift pin plate 20. The connectingmembers 24 are arranged at equal angular intervals on a circumferencenear the peripheral edge of the lift pin plate 20.

As shown in FIG. 4, the retaining plate 30 has a disk-like shape withthe through-hole 30 a formed in its central portion. The treatment fluidsupply pipe 40 is routed through the through-hole 30 a. A rotary cup 36is attached to the retaining plate 30 via a connecting member 38 asshown in FIG. 2A. When the lift pin plate 20, the treatment fluid supplypipe 40, and the bar-shaped nozzle 60 are at their lowered positions,the rotary cup 36 encircles the peripheral edge of the wafer W retainedby the retaining plate 30. As shown in FIGS. 2A and 2C, two fixedretaining members 37 are attached to the rotary cup 36 to retain thewafer W. The detailed function of the fixed retaining members 37 will bedescribed later. Instead of attaching the fixed retaining members 37 tothe rotary cup 36, they may be connected to the retaining plate 30, ormay be directly attached to the connecting member 38. If the fixedretaining members 37 are attached directly to the connecting member 38,the fixed retaining members 37 can be enhanced in strength against aforce applied from a horizontal direction.

A hollow rotating shaft 34 is attached to the central portion of thelower surface of the retaining plate 30 (i.e., the surface opposite tothe surface equipped with the rotary cup 36) to extend downwardtherefrom. The treatment fluid supply pipe 40 is accommodated in thecavity of the hollow rotating shaft 34. The rotating shaft 34 issupported by a bearing (not shown) and is rotated by the rotationaldriving unit 39 comprising an electric motor and so on. The rotationaldriving unit 39 rotates the rotating shaft 34, thus rotating theretaining plate 30 as well.

As shown in FIG. 4, three through-holes 30 b (connecting memberthrough-holes) are formed in the retaining plate 30. The connectingmembers 24 coupled to the lift pin plate 20 are each inserted slidablyin the through-hole 30 b. The connecting members 24 connect theretaining plate 30 and the lift pin plate 20 for their integral rotationwhile preventing relative rotation between them; the connecting members24 permit relative vertical movement between the retaining plate 30 andthe lift pin plate 20. The through-holes 30 b are arranged in theretaining plate 30 at equal angular intervals on a circumference on theretaining plate 30. In addition, on the lower surface of the retainingplate 30, the through-holes 30 b are provided with three accommodationmembers 32 having a cylindrical shape. The accommodation members 32extend downward from the lower surface of the retaining plate 30 andaccommodate the connecting members 24 extending downward from the lowersurface of the lift pin plate 20. The accommodation members 32 arearranged at equal angular Intervals on a circumference near a peripheralarea of the retaining plate 30.

Referring to FIG. 5, a further detailed description will be made for theconnecting members 24 extending downward from the lower surface of thelift pin plate 20, and the accommodation members 32 extending downwardfrom the lower surface of the retaining plate 30. As shown in FIG. 5,the cylindrical accommodation member 32 has an inside diameter slightlygreater than an outside diameter of the connecting member 24. Theconnecting member 24 can move in a longitudinal direction of theaccommodation member 32 (i.e., vertical direction in FIG. 5) in theaccommodation member 32. As shown in FIG. 2A, when the lift pin plate 20is at its lowered position, the connecting member 24 is completelyreceived in the accommodation member 32. Meanwhile, as shown in FIG. 2B,when the lift pin plate 20 is at its raised position, only a lowerportion of the connecting member 24 is received in the accommodationmember 32. The connecting member 24 passes through the through-hole 30 bin the retaining plate 30 and protrudes upward from the retaining plate30.

As shown in FIG. 5, a spring 26 is installed in the cavity of theaccommodation member 32 in a compressed state. The lower end of thespring 26 is connected to the bottom of the connecting member 24 whileits upper end is connected to the lower surface of the retaining plate30 in the vicinity of the through-hole 30 b. Thus, the spring 26 urgesthe connecting member 24 downward. In other words, force of the spring26 to return from the compressed state to an original state exerts adownward force upon the connecting member 24 (i.e., force to movedownward from the retaining plate 30).

As shown in FIGS. 2A and 2B, an outer cup 56 is provided outside therotary cup 36 to surround the retaining plate 30 and the rotary cup 36.In addition, a drainage tube 58 is connected to the outer cup 56. Duringcleaning of a wafer W, used cleaning liquid scatters outward from thewafer W due to its rotation. The scattered liquid will be received bythe outer cup 56 and is drained through the drainage tube 58.

As can be seen in FIG. 2A, a movable, substrate retaining member 31 forsupporting the wafer W from the lateral side of the wafer W is providedon the retaining plate 30. When the lift pin plate 20 is at its loweredposition as in FIG. 2A, the substrate retaining member 31 supports thewafer W from its lateral side. When the lift pin plate 20 is at itsraised position as shown in FIG. 2B, the substrate retaining member 31is separated away from the wafer W. The operation of the substrateretaining member 31 will be described more specifically with referenceto FIG. 2C. During wafer cleaning, the wafer W is retained by thesubstrate retaining member 31 and the two fixed retaining members (i.e.,non-movable, substrate-retaining members) 37. At this time, thesubstrate retaining member 31 presses the wafer W against the two fixedretaining members 37. That is, the substrate retaining member 31 appliesto the wafer W a leftward force to press the wafer W against the fixedretaining members 37. In the illustrated embodiment, since the wafer Wis retained by two fixed retaining members 37 and only one movablesubstrate-retaining member 31, the configuration for retaining the waferW can be more simplified as compared with a configuration employing aplurality of movable substrate retaining members 31 with no fixedretaining member 37.

Then, the configuration of the substrate retaining member 31 will bedetailed below referring to FIGS. 6 to 8.

FIG. 6 shows a state where the lift pin plate 20 is moving from itsraised position as in FIG. 2B to its lowered position as in FIG. 2A.FIG. 7 shows a state where the lift pin plate has moved more downwardfrom the state shown in FIG. 6. FIG. 8 shows a state where the lift pinplate 20 has moved further downward from the state of FIG. 7 to reachthe lowered position as shown in FIG. 2A.

As shown in FIGS. 6 to 8, the substrate retaining member 31 is supportedby the retaining plate 30 via an axle 31 a. More specifically, a bearingunit 33 is attached to the retaining plate 30, and an axle receivinghole 33 a of the bearing unit 33 receives the axle 31 a. The axlereceiving hole 33 a is an elongated hole extending in a horizontaldirection, and the substrate retaining member 31 can move horizontallyalong the axle receiving hole 33 a. The substrate retaining member 31can thus swing around the axle 31 a accommodated within the axlereceiving hole 33 a of the bearing unit 33.

A spring member 31 d such as a torsion spring is wound around the axle31 a of the substrate retaining member 31. The spring member 31 d isadapted to impart the substrate retaining member 31 a force to rotatethe substrate retaining member 31 around the axle 31 a in the clockwisedirection in FIGS. 6 to 8. Thus, when no force is applied to thesubstrate retaining member 31, the substrate retaining member 31inclines with respect to the retaining plate 30, as shown in FIG. 2B. Asubstrate retaining portion 31 b (described later) of the substrateretaining member 31, provided to hold the wafer W from its lateral side,then moves away from a central portion of the retaining plate 30.

The spring member 31 d has a linear portion extending outward from theaxle 31 a to an inner well 33 b of the bearing unit 33. The linearportion is engaged with the inner wall 33 b, thereby pushing back theaxle 31 a towards the center of the retaining plate 30. The axle 31 a isthus constantly pushed towards the center (leftward in FIGS. 6 to 8) ofthe retaining plate 30 by the linear portion of the spring member 31 d.When the movable substrate retaining member 31 and the fixed retainingmembers 37 are supporting a wafer W having a relatively small diameter,the axle 31 e is positioned in the axle receiving hole 33 a at aposition nearer to the center (left side) of the retaining plate 30, asshown in FIGS. 6 to 8. When the movable substrate-retaining member 31and the fixed retaining members 37 is supporting a wafer W having arelatively large diameter, the axle 31 a moves rightward along the axlereceiving hole 33 a from the position shown in FIGS. 6 to 8, against theforce applied by the linear portion of the spring member 31 d. Themagnitude of the wafer diameter (small/large diameter) here refers to amagnitude that falls within a tolerance range.

The substrate retaining member 31 has, in addition to the substrateretaining portion 31 b that retains the wafer W from its lateral side, apressure receiving member 31 c at the side opposite to the substrateretaining portion 31 b with respect to the axle 31 a. The pressurereceiving member 31 c is set between the lift pin plate 20 and theretaining plate 30. When the lift pin plate 20 is at or near the loweredposition, the lower surface of the lift pin plate 20 pushes thepressure-receiving member 31 c downward as shown in FIGS. 6 to 8.

While the lift pin plate 20 moves from its raised position to itslowered position, the lower surface of the lift pin plate 20 pushes thepressure receiving member 31 c downward. Then, the substrate retainingmember 31 rotates counterclockwise around the axle 31 a (in a directionshown by the arrows in FIGS. 6 to 8). This rotation of the substrateretaining member 31 around the axle 31 a renders the substrate retainingportion 31 b to approach the wafer W from its lateral side. The wafer Wis held from its lateral side by the substrate retaining member 31, asthe lift pin plate 20 reaches the lowered position as in FIG. 8. At thistime when the wafer W is held at its lateral side by the substrateretaining member 31, the wafer W is separated from the tip of each liftpin 22 and is held above the lift pins 22. Depending on the size of thewafer W, the axle 31 a may slide rightwards along the axle receivinghole 33 a from the position shown in FIGS. 6 to 8, against the forceapplied by the linear portion of the spring member 31 d. Therefore, thewafer W can be held from its lateral side without deforming nor damagingit even if the substrate retaining member 31 and the fixed retainingmembers 37 hold a relatively large wafer W, because the substrateretaining member 31 can shift in the horizontal direction.

By employing such substrate retaining member 31, the substrate cleaningapparatus 10 do not need a special driving mechanism (motive energysource) for driving a substrate retaining member 31. The substrateretaining member 31 of the retaining plate 30 can retain and release awafer W just by vertically moving the lift pin plate 20 using a verticaldriving unit 50 (described later). The configuration of the substratecleaning apparatus 10 can thus be simplified. It also reduces the timelag between the timing of raising and lowering of the lift pin plate 20and the timing of the action of the substrate retaining member 31,whereby improving throughput.

As shown in FIGS. 2A and 23, the treatment fluid supply pipe 40 isarranged to pass through both the through-hole 20 a in the lift pinplate 20 and the through-hole 30 a in the retaining plate 30. Thetreatment fluid supply pipe 40 is arranged such that it does not rotatewhen the lift pin plate 20 and the retaining plate 30 rotate. Extendingthrough the treatment fluid supply pipe 40 in the axial directionthereof are: a liquid supply passage 40 a through which, as a cleaningliquid, a chemical liquid such as DHF (dilute hydrofluoric acid)solution and SC1 (Standard Clean 1) solution, and a rinse liquid such asDIW (deionized water) flows; and a gas supply passage 40 b through whicha gas, such as an inert gas, e.g., N₂ gas flows. The bar-shaped nozzle60 which will be detailed later is attached to the upper end of thetreatment fluid supply pipe 40.

As shown in FIGS. 2A, 2B, and 9, the vertical driving unit 50 isconnected with the treatment fluid supply pipe 40 via a connectingmember 52. The vertical driving unit 50 is configured to move thetreatment fluid supply pipe 40 vertically. That is, by raising/loweringthe connecting member 52, the vertical driving unit 50 moves thetreatment fluid supply pipe 40 and bar-shaped nozzle 60 connected to theconnecting member 52. More specifically, the vertical driving unit 50raises/lowers the treatment fluid supply pipe 40 and the bar-shapednozzle 60 between their lowered positions as in FIG. 2A and their raisedpositions as in FIG. 2B.

As shown in FIG. 9, the treatment fluid supply pipe 40 is furtherattached with a first interlocking member 44. Three rod-shaped secondinterlocking members 46 are connected to the first interlocking member44 to extend upward therefrom. The second interlocking members 46 arearranged to correspond to the connecting members 24 extending downwardfrom the lift pin plate 20. The outer diameter of the secondinterlocking member 46 is smaller than the inner diameter of thecylindrical accommodation member 32. That is to say, each secondinterlocking member 46 is arranged to contact the bottom of oneconnecting member 24 so that the second interlocking member 46 can pushthe connecting member 24 upward within the accommodation member 32, asshown in FIG. 2B.

Accordingly, when the vertical driving unit 50 moves the treatment fluidsupply pipe 40 upward from the state shown in FIG. 2A, the firstinterlocking member 44 and second interlocking members 46 joined withthe treatment fluid supply pipe 40 also moves upward so that the secondinterlocking members 46 push the connecting members 24 upward inside theaccommodation members 32, whereby the lift pin plate 20 moves integrallywith the treatment fluid supply pipe 40 so that the lift pin plate 20,the treatment fluid supply pipe 40, and the bar-shaped nozzle 60 thusreach their raised positions as in FIG. 2B. On the other hand, when thevertical driving unit 50 moves the treatment fluid supply pipe downwardfrom the state shown in FIG. 2B, since the spring 26 set within theaccommodation member 32 constantly applies a downward force to theconnecting member 24, the connecting member 24 descends downwardintegrally with the interlocking member 46 with its bottom being incontact with the top of the second interlocking member 46. The lift pinplate 20, the treatment fluid supply pipe 40, and the bar-shaped nozzle60 thus reach their respective lowered positions as in FIG. 2A.

The lift pin plate 20 adjoins the retaining plate 30 when the lift pinplate 20 is positioned at its lowered position, as shown in FIG. 2A. Inthe illustrated embodiment, the lift pin plate 20 is rested on andsupported by the retaining plate 30. On the other hand, the lift pinplate 20 is separated from the retaining plate 30 when the lift pinplate 20 is positioned at its raised position, as shown in FIG. 2B. Thewafer W is then supported by the lift pins 22 and can be removedtherefrom.

As mentioned above, the liquid treatment apparatus includes aninterlocking mechanism having the first interlocking member 44 and thethree second interlocking members 46 for integrally raising and loweringthe lift pin plate 20, the treatment fluid supply pipe 40, and thebar-shaped nozzle 60. The liquid treatment apparatus also includes alifting mechanism for integrally raising and lowering the lift pin plate20, the treatment fluid supply pipe 40, and the bar-shaped nozzle 60relative to the retaining plate 30 by employing the first interlockingmember 44, the three second interlocking members 46, the verticaldriving unit 50 and the connecting member 52.

Next, the configuration of the bar-shaped nozzle 60 will be describedbelow with reference to FIGS. 2A, 2B, 9, and 10. The bar-shaped nozzle60 includes a bar-shaped portion 60A and a central portion 60B. Thebar-shaped nozzle 60 is attached via the central portion 60B to theupper end of the treatment fluid supply pipe 40. The central portion 60Balso serves as a covering member for covering the through-hole 20 a inthe lift pin plate 20. The bar-shaped portion 60A extends from thecentral portion 60B in a radially outward direction of the lift pinplate 20, that is, a radially outward direction of the wafer W, andterminates slightly before an imaginary circle along which the lift pins22 are arranged so as not to interfere with the pins 22.

As shown in FIG. 10, the bar-shaped portion 60A has a cross section likean airfoil. In this liquid treatment apparatus, the wafer W rotates in adirection of the arrow R shown in FIG. 10( b) with respect to thebar-shaped portion 60A. The rotation of the wafer W generates anairstream flowing in the direction of the arrow R in the space betweenthe lower surface of the wafer W and the lift pin plate 20. Thisairstream passing through the space above the bar-shaped portion 60Aimproves the flow of the liquid. More specifically, as the airstreampasses through a space between the back side of the bar-shaped portion60A and the wafer W, the airstream will be accelerated by the throttleeffect and deflected in a direction towards the lower surface of thewafer W. Such airstream assists the treatment liquid (e.g., a chemicalliquid) that has collided with the lower surface of the wafer W tospread more smoothly over the lower surface. In addition, since thebar-shaped portion 60A has a cross section like an airfoil, vibration ofthe bar-shaped portion 60A due to the airstream can be suppressed to aminimum.

The upper surface of the bar-shaped portion 60A is provided with aplurality of ejection ports 61 (first ejection ports) arranged in thelongitudinal direction of the bar-shaped portion 60A. Their arrangementpitch may be between about 1 and 2 mm, and the hole diameter may bebetween about 0.2 and 0.5 mm. The central portion 60B is also providedwith a plurality of ejection ports 62 (second ejection ports).

The treatment fluid supply pipe 40 has, at its upper end, a head 41 ofan enlarged diameter. The central portion 60B of the bar-shaped nozzle60 includes hollow engaging protrusions 63 a and 63 b on a lower surfaceof the central portion 60B. The liquid supply passage 40 a and the gassupply passage 40 b extending through the treatment fluid supply pipe 40are opened at the upper surface of the head 41, into which the engagingprotrusions 63 e and 63 b are fitted, respectively. A truncated conicalcover 65 is attached to the lower surface of the central portion 60B toprovide the central portion 60B with a function of a covering member forcovering the through-hole 20 a in the lift pin plate 20. The rim of thecover 65 is located above the circular protrusion 20 b (see FIGS. 2A and3) formed around the through-hole 20 a in the lift pin plate 20. In thisembodiment, the cover 65 is integrated with the central portion 60B ofthe bar-shaped nozzle 60 by jointing the head 41 of the treatment fluidsupply pipe 40 and the central portion 60B together via bolts 64, withthe cover 65 interposed between the central portion 60B and the head 41of the treatment fluid supply pipe 40. The cover 65 may instead beinitially formed integrally with the central portion 60B. Although thecover 55 is preferred to have a truncated conical shape, the shape ofthe cover 65 is not limited to that as illustrated, and any shape ispossible as long as it covers the through-hole 20 a and prevents liquidentering. Further, the cover 65 may be formed integrally with the head41 of the treatment fluid supply pipe 40. The head 41 attached with thecover can be jointed with the central portion 608 to give the centralportion 60B the function of a covering member.

The central portion 60B of the bar-shaped nozzle 60A houses a liquidpassageway 66 a and a gas passageway 66 b which respectivelycommunicates with the liquid supply passage 40 a and the gas supplypassage 40 b. The liquid passageway 66 a and the gas passageway 66 bextend radially outward to the distal end portion of the bar-shapedportion 60A of the bar-shaped nozzle 60 (along the longitudinaldirection of the bar-shaped nozzle 60), horizontally and in parallel toeach other.

As shown in FIG. 10( b), each ejection port 61 on the bar-shaped portion60A is connected to a liquid ejecting passage 67 a and a gas ejectingpassage 67 b. The liquid ejecting passage 67 a and the gas ejectingpassage 67 b are respectively connected with the liquid passageway 56 aand the gas passageway 66 b. The liquid ejecting passage 67 a and thegas ejecting passage 67 b meet at the upper surface or near the uppersurface of the bar-shaped portion 60A (i.e., at the ejection port 61 orat its vicinity).

As shown in FIG. 10( c), each ejection port 62 on the central portion60B is connected to a liquid-ejecting passage 68 a and a gas-ejectingpassage 68 b. The liquid-ejecting passage 68 a and the gas-ejectingpassage 68 b is respectively connected with the liquid passageway 66 aand the gas passageway 66 b. The liquid ejecting passage 68 a and thegas ejecting passage 68 b meet below the upper surface of the centralportion 60B and the combined passage is lead to the ejection port 62.The aperture diameter of the ejection port 62 is larger than that of theejection port 61.

Referring to FIG. 2A, the liquid supply passage 40 a and gas supplypassage 40 b in the treatment fluid supply pipe 40 are respectivelyconnected to a liquid supply mechanism 70 and a gas supply mechanism 80.The liquid supply mechanism 70 includes a first liquid supply unit 70 afor supplying at least one kind of chemical liquid (one liquid in thisembodiment) to the liquid supply passage 40 a, and a second liquidsupply unit 70 b for supplying DIW (deionized water) as a rinsing liquidto the liquid supply passage 40 a. The first liquid supply unit 70 a isconnected to a chemical liquid supply source (CHM) 71 a containing DHFor SC1, etc. via a line 74 a. The line 74 a comprises, from the upstreamside, a variable throttle valve 72 a and an open/close valve 73 a.Similarly, the second liquid supply unit 70 b is connected to a DIWsupply source 71 b via a line 74 b, and the line 74 b is provided with avariable throttle valve 72 b and an open/close valve 73 b from theupstream side. The lines 74 a and 74 b meet at a downstream of theopen/close valves 73 a and 73 b, and then connected to the liquid supplypassage 40 a. Open/close valves denoted by reference numbers 75 and 76are used to drain liquids remained in the lines 74 a and 74 b. If it isnecessary to supply two or more kinds of chemical liquids to the liquidsupply passage 40 a, for example, if SC1 cleaning and DHF cleaning is tobe executed successively, an additional liquid supply unit having asimilar configuration as that of the first liquid supply unit 70 a maybe provided in parallel.

The gas supply mechanism 80 is provided to supply gas such as an inertgas (in the illustrated embodiment, N₂ gas) to the gas supply passage 40b. The gas supply mechanism 80 and an N₂ gas supply source 81 isconnected to with a line 84 a, and the line 84 a is provided from theupstream side with a variable throttle valve 82 and an open/close valve83.

The substrate cleaning apparatus 10 further includes a configuration forsupplying treatment fluid to the upper surface of the wafer W retainedby the retaining plate 30. In the illustrated embodiment, the substratecleaning apparatus 10 has a chemical liquid supply nozzle 91 forejecting chemical liquid to the upper surface of the wafer W; atwo-fluid nozzle 92 for Jetting a mist of a fluid mixture including DIWand N₂ gas to the upper surface of the wafer W. The chemical liquidsupply nozzle 91 and the two-fluid nozzle 92 can be moved by a nozzledriving mechanism 93 from the center of the wafer W to its peripheraledge. In other words, the nozzles can supply the treatment fluid whilescanning the upper surface of the wafer W. The nozzle driving mechanism93 can also move the chemical liquid supply nozzle 91 and the two-fluidnozzle 92 to a standby position (not shown) outside the outer cup 56.The chemical liquid supply source 71 a can feed chemical liquid to thechemical liquid supply nozzle 91 at a controlled flow rate through avariable throttle valve 94 a and an open/close valve 95 a. Similarly,the DIW supply source 71 b and the N₂ gas supply source 81 can feed DIWand N₂ gas to the two-fluid nozzle 92 at controlled flow rates bythrough variable throttle valves 94 b, 94 c and open/close valves 95 b,95 c. The nozzle driving mechanism 93 may be a type that uses a pivotalarm holding a nozzle(s) at its distal end, or a type that uses an armguided by a guide rail for translational motion and holding a nozzle(s)at its distal end. Further, a single nozzle driving mechanism (93) maydrive both the chemical liquid supply nozzle 91 and the two-fluid nozzle92, or alternatively, the chemical liquid supply nozzle 91 and thetwo-fluid nozzle 92 may each have an independent nozzle-drivingmechanism.

The substrate cleaning apparatus 10 includes a controller 100 thatcontrols the whole operation of the apparatus. The controller 100controls operation of all functional components of the substratecleaning apparatus 10 (e.g., the rotational driving unit 39, thevertical driving unit 50, the open/close valves, the variable throttlevalves, the nozzle driving mechanism 93, etc.). The controller 100 canbe implemented with hardware such as a general-purpose computer, and aprogram as software for controlling the computer (apparatus controlprogram, processing recipe, etc.). The software may be stored in ahard-disk drive or other storage medium fixedly provided in thecomputer, or may be stored in a storage medium removably set in thecomputer such as a CD-ROM, DVD, flash memory. Such a storage medium isdenoted with reference number 106. Upon receipt of instructions from auser interface (not shown), a processor 107 calls up a requiredprocessing recipe from the storage medium 106 and executes the recipe.The controller 100 thereby controls and operates the functionalcomponents of the substrate cleaning apparatus 10 to perform apredetermined process (treatment). Alternatively, the controller 100 maybe a system controller that controls the whole operations of the liquidtreatment system shown in FIG. 1.

Next, the manner of ejecting treatment fluids (processing fluids) fromthe bar-shaped nozzle 50 is described. There are two ejection modes setfor the bar-shaped nozzle 60 to eject the treatment fluid.

(First Ejection Mode)

In a first ejection mode, a chemical liquid such as DHF is fed to theliquid supply passage 40 a of the treatment fluid supply pipe 40 whileno gas is fed to the gas supply passage 40 b. As shown in FIG. 11( b),the chemical liquid is fed to the bar-shaped portion 60A through theliquid passageway 66 a and the liquid ejecting passage 62 a, and thenejected toward the lower surface of the wafer W from the ejection ports61. The liquid-ejecting passage 57 a is inclined to the rotatingdirection of the wafer W, and the ejection port 61 is formed so as notto change the direction of liquid flow in the liquid ejecting passage 67a. Therefore, the chemical liquid is ejected obliquely from the ejectionport 61. The vector representing the ejecting direction of the chemicalliquid has a component of the rotating direction of the wafer W. Byejecting the chemical liquid to the wafer W in such a manner, bouncing(splash-back) of the chemical liquid upon collision against the lowersurface of the wafer W can be suppressed. This reduces waste of thetreatment liquid and increases efficiency of treatment liquid usage.

The plurality of ellipses in FIG. 12 each represent an area where anejected liquid covers on the lower surface of the wafer W at the instantof reaching the surface (this area is hereinafter also referred to as“spot”). After reaching the lower surface of the wafer W, the chemicalliquid ejected from the ejection port 61 spreads on the surface due tofactors such as a centrifugal force of the rotation of the wafer W, andthe pressure of ejecting from the ejection port 61. In a plan view, eachejection port 61 in the bar-shaped portion 60A ejects the liquid in atangential direction of a circle that passes through the particularejection port 61 and has its center at the wafer center. Thus, a pitch Pbetween the centers of the elliptical spots is equal to the arrangementpitch of the ejection ports 61. Since the liquid diffuses after beingejected, a minor axis of each ellipse has a length “B” that is greaterthan a diameter of the ejection port 61. A major axis of the ellipse hasa length “A” much greater than the diameter of the ejection port 61because the liquid is ejected from the ejection port 61 at an angleinclined to the direction of the wafer rotation. Adjacent ellipticalspots form an overlapped area with a certain length L.

The ejection port 62 of the central portion 60B in the first ejectionmode is configured to turn the flow of the chemical liquid from theliquid ejecting passage 67 a into a vertically upward direction. Thechemical liquid is ejected vertically upward from the ejection port 62.The chemical liquid thus forms a circular spot on the lower surface ofthe wafer W. The reason for ejecting the chemical liquid verticallyupward is that the part of the wafer W above the central portion 50B hasa low circumferential velocity and it is thus not so advantageous toeject the chemical liquid obliquely. Additionally, oblique ejecting ofthe chemical liquid may rather reduce uniformity of the treatment nearthe wafer center.

FIG. 11( a) shows the spots formed by the chemical liquid ejected fromthe ejection ports 61, 62 onto the lower surface of the wafer W at theinstant of reaching the lower surface. The small white circles denotethe ejection ports 61, “x” marks denote the centers of the ejectionports 62, the white ellipses denote the spots formed by the chemicalliquid ejected from the ejection ports 61, and the larger white circlesdenote the spots formed by the liquid ejected from the ejection ports62.

At least some (in the illustrated embodiment, five) of the ejectionports 61 positioning at the distal end portion on the bar-shaped portion60A are oriented in a direction shifted radially outward (see arrow D2)from the tangential direction (arrow D1) at an angle θ, in a plan view.These distal ejection ports 61 form flows of chemical liquid flowingtowards outside of the wafer W, whereby unnecessary substances andcontaminants having been removed from the lower surface of the wafer Ware flushed out of the wafer W. As an example of such configuration, themost distal ejection port 61 may have the maximum angle, and an angle θof the ejection ports 61 may decrease as it approaches the proximal end.An ejection port 61 at a certain position counted from the outermostport 61, in this case the sixth one, can be adapted to have an angle θof 0 degrees. If the angles θ are not zero, the overlapping length Lbetween the adjacent elliptical spots are smaller.

Depending on the kind of treatment, the overlapping length (radiallength) L between the adjacent elliptical spots may possibly affectin-plane uniformity of the surface being treated. In a case where suchproblem is expected, it is preferable to change the ejecting pressure(force) of the chemical liquid from the ejection port 61 by adjustingthe variable throttle valve 72 a. If the ejecting pressure (force) ofthe chemical liquid is sufficiently high, the liquid spreads out in aburst immediately after reaching the lower surface of the wafer W (atthe instant of liquid reaching the surface, the size of spots is notdifferent so much depending on the ejecting pressure). The size ofelliptical spots thus substantially increases, thereby to produce thesame effect as that obtained by increasing the overlapping length L. Theejecting (discharging) pressure of the liquid can be changed in apulse-like manner as by alternating high and low pressure, or may bechanged continuously in accordance with a predetermined control curvesuch as a sine curve.

Alternatively or in addition to the above, the chemical liquid may beejected from the ejection port 61 while moving the bar-shaped nozzle 60.The bar-shaped nozzle 50 may be moved by using a horizontal movingmechanism 54 mounted at the bottom of the vertical driving unit 50(schematically depicted with a dashed line in FIG. 9). A functionsimilar or equivalent to that of the horizontal moving mechanism 54 canbe incorporated in the connecting member 52 as an alternative method.The horizontal moving mechanism 54 slightly shifts the treatment fluidsupply pipe 40 in the horizontal direction to move the bar-shaped nozzle60 in the longitudinal direction of the bar-shaped portion 60A. As theposition of the overlapped areas between the adjacent elliptical spotschanges, uniformity of the treatment can be improved. The movingdistance of the bar-shaped nozzle 60 may be the same as or less than thearrangement pitch of the ejection ports 61 on the bar-shaped nozzle 60.The horizontal moving mechanism 54 can be constructed with a ball screwdriven by an electric motor for example. Any other mechanism can beadopted as long as it is suitable of linear driving for a slight amount.

Referring to FIG. 11( a), as can be seen from arc C depicted with dashedlines, the spot formed by the chemical liquid that has been ejected fromthe ejection port 62 closest to the bar-shaped portion 60A, and the spotformed by the chemical liquid that has been ejected from the ejectionport 61 closest to the central portion 60B, form an overlapped area. Thelength of this overlapped area can also be changed by controlling theejecting pressure of the chemical liquid.

The ejection ports 61 do not need to be strictly arranged on a radius ofthe wafer (i.e., on a straight line passing through the center of thewafer) as long as the spots formed by the chemical liquid ejected fromthe ejection ports 61 are generally aligned in a radial direction of thewafer. In the configuration shown in FIG. 11( a), only the ejectionports 62 are exactly positioned in the radial direction of the wafer(i.e., on the straight line passing through the center of the wafer);while the ejection ports 61 are arranged on a straight line parallel toand slightly shifted from the line passing the wafer center.Alternatively, all of the ejection ports 61, 52 may be arranged on onestraight line in a plan view, for example, on a straight line passingthrough the wafer center (see FIG. 16( a)). In another embodiment, allspots formed by the chemical liquid ejected from the ejection ports 61,62 may be arranged on one straight line, for example, on a straight linepassing through the wafer center (see FIG. 16( b)). The spots formed bythe chemical liquid ejected from the ejection ports 61, 62 may form abroken line (see FIG. 16( c)). The arrangement line on which theejection ports 61 are arrayed may be curved to some degree. Anyway, itis sufficient if the plurality of ejection ports 61 are arrayed in anarea extending from a position opposing the central portion of the waferW (substrate) to a position opposing the peripheral portion of thewafer.

(Second Ejection Mode)

In a second ejection mode, DIW is fed to the liquid supply passage 40 ain the treatment fluid supply pipe 40, and N₂ gas is fed to the gassupply passage 40 b. At the bar-shaped portion 60A, as shown in FIG. 13(a), DIW is guided to each ejection port 61 via the liquid passageway 66a and the liquid ejecting passage 57. Similarly, N₂ gas is guided toeach ejection port 61 via the gas passageway 66 b and the gas ejectingpassage 67 b. The DIW and the N₂ gas collide at the ejection port 61 toform a mist of a fluid mixture including the DIW and the N₂ gas, thatis, a two-fluid spray. Due to the collision between the DIW and the N₂gas, the two-fluid spray blows upward while spreading in a fan-likefashion. The collision energy of the two-fluid spray cleans the lowersurface of the wafer W. In this case, the vector representing theejecting direction (principal direction) of the two-fluid spray isdirected vertically upward. The vector substantially does not have acomponent of the rotational direction of the wafer W. This is preferablein this mode since the cleaning effect of the two-fluid spray relies onthe collision energy or the two-fluid spray. It is also preferable ifthe vector representing the ejecting direction (principal direction) ofthe two-fluid spray has a component of the direction opposite to thedirection of the wafer W rotation.

In the second ejection mode, since the ejection port 62 of the centralportion 60B is formed to turn the flows of the DIW and the N₂ gassupplied from the liquid ejecting passage 68 a and the gas ejectingpassage 68 b vertically upward, the two-fluid spray ejected from theejection port 62 moves upward while spreading in a fan-like fashion.

As with the first ejection mode, the two-fluid spray may be ejected ontoupon the lower surface of the wafer W while changing both or one of theDIW ejecting pressure and the N₂ gas ejecting pressure by adjusting theopening of the variable throttle valves 72 b, 82.

Next, a series of process steps executed by the substrate cleaningapparatus 10 will be described below.

First, the lifting mechanism moves the lift pin plate 20, the treatmentfluid supply pipe 40, and the bar-shaped nozzle 60, to their respectiveraised positions shown in FIG. 2B. Next, as shown by double-dashed linesin FIG. 2B, a wafer W is carried into the cleaning apparatus 10 fromoutside by the transport arm 104. The wafer W is placed on the lift pins22 of the lift pin plate 20.

The vertical driving unit 50 next moves the treatment fluid supply pipe40 and the bar-shaped nozzle 60 from their raised positions to theirlowered positions. At this time, since the spring 26 housed in theaccommodation member 32 constantly applies a downward force to theconnecting member 24, the lift pin plate 20 also moves downward with thetreatment fluid supply pipe 40 to the downward movement position. Thelower surface of the lift pin plate 20 then pushes the pressurereceiving member 31 c of the substrate retaining member 31 downward fromthe state shown in FIG. 6. The substrate retaining member 31 rotatesaround the axle 31 a in the counterclockwise direction in FIG. 6. Thesubstrate retaining portion 31 b of the substrate retaining member 31thus moves towards the wafer W from the lateral side of the wafer (seeFIG. 7), and the substrate retaining member 31 thus retains the wafer Wfrom its lateral side (see FIG. 8). At the point of time when the waferW is just retained from its lateral side by the substrate retainingmember 31, the wafer W is lifted to be separated upward from the liftpin 22. Normally, the wafer W is retained by the retaining plate 30 insuch a manner that its “front surface” (the surface on which devices areto be formed) comes to the “upper surface” and its “back surface” comesto the “lower surface” (the surface on which no devices are to beformed). In this disclosure, the term “upper surface” (or “lowersurface”) simply means a face that is facing upward (downward) at aparticular point of time.

After the lift pin plate 20, the treatment fluid supply pipe 40, and thebar-shaped nozzle 60 have reached their respective lowered positionsshown in FIG. 2A, the nozzle driving mechanism 93 is activated to movethe chemical liquid supply nozzle 91 to a position above the center ofthe upper surface of the wafer W. Next, the rotational driving unit 39is activated to rotate the retaining plate 30. At this time, since theconnecting members 24 extending downward from the lower surface of thelift pin plate 20 is inserted within the accommodation members 32extending downward from the lower surface of the retaining plate 30, thelift pin plate 20 rotates interlockingly with the rotation of theretaining plate 30, whereby rotating the wafer W as well. The treatmentfluid supply pipe 40 and the bar-shaped nozzle 60 connected theretoremain still and does not rotate during the rotation.

Next, the chemical liquid supply nozzle 91 located above the wafercenter starts supplying the chemical liquid such as DHF to the uppersurface of the wafer W with the wafer W being rotated. While thechemical liquid is supplied to the upper surface of the wafer W, thenozzle driving mechanism 93 moves the chemical liquid supply nozzle 91radially outward over the wafer W until the nozzle 91 reaches the waferedge. The upper surface of the wafer W is thus cleaned with the chemicalliquid by the so-called scanning method.

Simultaneously with the start of cleaning the upper surface of the waferW with the chemical liquid, the bar-shaped nozzle 60 supplies a chemicalliquid (the same chemical liquid as that supplied to the upper surfaceof the wafer W) onto the lower surface of the rotating wafer W in thefirst ejection mode, whereby the lower surface of the wafer W issubjected to chemical cleaning.

After the chemical liquid cleaning, a liquid droplet treatment (process)using a liquid-gas fluid mixture is conducted to remove particles. Thetwo-fluid nozzle 92 is moved to a position above the center of the uppersurface of the wafer W by the nozzle driving mechanism 93, and the waferW starts rotating. The two-fluid nozzle 92 supplies the upper surfacewith a two-fluid spray which is the fluid mixture of DIW and N₂ gaswhile being moved radially outward to the wafer edge by the nozzledriving mechanism 93. Thus, the liquid droplet treatment of the uppersurface of the wafer W is performed in the so-called scanning method.

Simultaneously with the start of the liquid droplet treatment of theupper surface of the wafer W, the bar-shaped nozzle 60 ejects or jets atwo-fluid spray which is the fluid mixture of DIW and N₂ gas to thelower surface of the rotating wafer W in the second ejection mode. Thelower surface of the wafer W is thus also subjected to liquid droplettreatment. Since the liquid droplet treatment provides a strong physicalcleaning effect, the chemical liquid used in the preceding treatment andparticles can be removed efficiently.

After the liquid droplet treatment, the wafer W is rotated for drying.

When the successive processes are all completed, the vertical drivingunit 50 moves the treatment fluid supply pipe 40 and the bar-shapednozzle 60 from their lowered positions to raised positions. The secondinterlocking members 46 push the connecting members 24 to raise the liftpin plate 20 from its lowered position to its raised positioninterlockingly with the raising of the treatment fluid supply pipe 40.At the same time, the biasing force of the spring 26 rotates thesubstrate retaining member 31 around the axle 31 a in thecounterclockwise direction in FIG. 6 (i.e., in a direction opposite tothe arrow in FIG. 6). The substrate retaining portion 31 b leaves fromthe side of the wafer W and the lower surface of the wafer W is thensupported by the lift pins 22.

After the lift pin plate 20, the treatment fluid supply pipe 40, and thebar-shaped nozzle 60 have reached their respective raised positions asshown in FIG. 2B, the wafer W rested on the lift pins 22 is removed fromthe lift pins 22 by the transport arm 104. The wafer W, after beingremoved by the transport arm 104, is carried to the outside of thesubstrate cleaning apparatus 10.

In the foregoing embodiment, due to the use of the nozzle having theplurality of ejection ports 61 arrayed along a line connecting aposition opposing the central portion of the wafer W and a positionopposing the peripheral portion of the wafer W, the lower surface of thewafer W can be treated with high in-plane uniformity. The amount ofconsumption of treatment fluid(s) can be reduced. The lower surface ofthe wafer W can be washed or flushed uniformly. Additionally, thedirection in which the liquid is ejected from the ejection ports 61 isinclined in the rotational direction of the wafer W, in other words, theejection ports 61 are formed such that the direction in which thetreatment liquid is ejected has a component of the rotating direction ofthe wafer W. This suppresses splashing of the treatment liquid upon itscollision with the lower surface of the wafer W and reduces wastethereof. Further, generation of particles due to re-adhesion of thesplashed liquid can be suppressed. Since the ejection ports in thedistal end portion of the nozzle is directed outward, the treatmentliquid supplied onto the wafer surface can be flushed out of the wafersurface.

Further, in the Foregoing embodiment, the lower surface of the wafer Wcan be treated concurrently with the upper surface of the wafer W, witha high in-plane uniformity substantially equivalent to that of thetreatment of the upper surface. Thus, throughput can be improved whileachieving a treatment result of high quality.

The lift pin plate 20, the treatment fluid supply pipe 40, and thebar-shaped nozzle 60 move vertically relative to the retaining plate 30,and the lift pins 22 for supporting the lower surface of the wafer W areprovided on the lift pin plate 20. In addition, the cover 65 is providedbetween the treatment fluid supply pipe 40 and the bar-shaped nozzle 60to cover the through-hole 20 a in the lift pin plate 20. Since the cover65 covers the through-hole 20 a of the lift pin plate 20, the cleaningliquid is prevented from entering the through-hole 20 a for insertingthe treatment fluid supply pipe 40. Further, in the foregoingembodiment, the lift pins 22 are provided on the lift pin plate 20. Ascompared with a conventional apparatus having lift pins to be retractedinto through-holes formed in a bottom plate, the apparatus in theforegoing embodiment is advantageous in that there will be less cleaningliquid left on the lift pins 22 after drying a wafer W, which preventsthe cleaning liquid from re-adhering to the lower surface of the wafer Wafter cleaning. This is because the lift pins 22 rotate integrally withthe lift pin plate 20. Since the lift pins 22 rotates integrally withthe lift pin plate 20, adhesion of droplets of the cleaning liquid ontothe lift pins 22 can be suppressed, whereby the re-adhering of thecleaning liquid to the lower surface of the cleaned wafer W can beprevented more effectively.

In the foregoing embodiment, since the treatment fluid supply pipe 40and the bar-shaped nozzle 50 move vertically together with the lift pinplate 20, the cover 65 covers the through-hole 20 a of the lift pinplate 20 also during vertical movement of the treatment fluid supplypipe 40 and the lift pin plate 20, and the cleaning liquid is preventedfrom entering the through-hole 20 a more effectively.

Since the rotary cup 36 is provided on the retaining plate 30, thecleaning liquid is prevented from scattering externally from therotating wafer W during cleaning. Further, due to the substrateretaining member 31 attached on the retaining plate 30, the wafer W canbe stably retained during rotation by supporting the wafer W from itslateral side.

The foregoing description of the embodiment describes a case where theejection ports 61 inject fluid such as a chemical liquid or DIW whilechanging the position of the bar-shaped nozzle 60 by the horizontalmoving mechanism 54. This case is further describes in detail belowreferring to FIG. 17.

First, the reason for shifting the lateral position of the bar-shapednozzle 60 while ejecting the treatment liquids from the ejection ports61 will be described. It is assumed that a treatment liquid is suppliedfrom the chemical liquid supply source 71 a or the DIW supply source 71b to the bar-shaped nozzle 60 at a constant (fixed) pressure. In such acase, as the number of ejection ports 61 increases and/or the holediameter of the ejection ports 61 increases, the velocity of thetreatment liquid ejected from each ejection port 61 decreases. Under thecondition that the feed pressures of the chemical liquid supply source71 a and the DIW supply source are fixed, the number of ejection ports61 and their hole diameter each need to be limited in order to maintainthe velocity of the liquid ejected (jetted) from each ejection port 61at a predetermined desired value. When the number of ejection ports 61and their hole diameter each are limited as above, two adjacent spotsformed on the lower surface of the wafer W by the treatment liquidconcurrently ejected from two adjacent ejection ports 61 may not overlapwith each other, in a plan view. In such case, it is advantageous toshift the lateral position of the bar-shaped nozzle 60 during theejection of the treatment liquid from the ejection ports 61.

FIG. 17 shows schematic plan views showing states of when the liquid isejected from the ejection ports 61 while shifting the position of thebar-shaped nozzle 60. As shown in FIG. 17( a), at least some of theplurality of ejection ports 61 are arranged at a predetermined pitch Palong the horizontal line on which the plurality of ejection ports 61lay. The arrow L in FIG. 17( a) denotes a direction in which thehorizontal line connecting the arranged ejection ports 61 extends(hereinafter, this direction is referred to as the arrangement directionL), FIG. 17( b) is a schematic plan view that shows a state in which theposition of the bar-shaped nozzle 60 is shifted through one third (⅓) ofthe arrangement pitch P in the arrangement direction L, from theposition in FIG. 17( a) towards the peripheral edge of the wafer W. FIG.17( c) is a schematic plan view that shows a state in which the positionof the bar-shaped nozzle 60 is shifted by one third of the arrangementpitch P in the arrangement direction L, from the position in FIG. 17( b)towards the peripheral edge of the wafer W.

First, the ejection ports 61 eject a treatment liquid (processingliquid) to the lower surface of the wafer W in the first ejection modewith the bar-shaped nozzle 60 placed at a predetermined position (firstposition). FIG. 17( a) shows a spot S1 formed on the lower surface ofthe wafer W by the treatment liquid ejected from each ejection port 61at the moment the treatment liquid reaches the lower surface of thewafer W. In FIG. 17( a), the spot S1 is depicted as an elliptical regionsurrounded by a solid line. The ejection of the treatment liquid fromthe bar-shaped nozzle 60 in the first position is continued for a timeperiod corresponding to at least one revolution (360 degrees) of thewafer W.

Next, as shown in FIG. 17B, the horizontal moving mechanism 54 shiftsthe bar-shaped nozzle 60 through one third of the arrangement pitch P,in the arrangement direction L towards the edge of the wafer W. Then atthis position (second position), each ejection port 61 ejects treatmentliquid to the lower surface of the wafer W in the first ejection mode.In FIG. 17( b), depicted by a solid line is a spot S2, which is formedon the lower surface of the wafer W by the treatment liquid ejected fromeach ejection port 61 at the moment the treatment liquid reaches thelower surface of the wafer W, when the bar-shaped nozzle 60 ispositioned at the second position. In FIG. 17( b), the spot S1 formedwhen the bar-shaped nozzle 60 is in the first position is depicted bydotted lines. The second position is set such that one spot S1 formedwhen the bar-shaped nozzle 60 is in the first position and one spot S2formed when the bar-shaped nozzle 60 is in the second position partiallyoverlap in a plan view. The ejection of the treatment liquid from thebar-shaped nozzle 60 in the second position is continued for a timeperiod corresponding to at least one revolution (360 degrees) of thewafer W.

Next, as shown in FIG. 17( c), the position of the bar-shaped nozzle 60is further shifted by the horizontal moving mechanism 54 through onethird of the arrangement pitch P, towards the edge of the wafer W in thearrangement direction L. Then at this position (third position), thetreatment liquid is ejected from each ejection port 61 to the lowersurface of the wafer W in the first ejection mode. In FIG. 17( c),depicted by a solid line is a spot S3, which is formed on the lowersurface of the wafer W by the treatment liquid ejected from eachejection port 61 at the moment the treatment liquid reaches the lowersurface of the wafer W, when the bar-shaped nozzle 60 is positioned atthe third position. In FIG. 17( c), the spot S1 and S2 formed when thebar-shaped nozzle 60 is in the first and second positions are depictedby dotted lines. The third position is set such that, in a plan view,one spot S3 partially overlaps with both one spot S1 and one spot S2that were respectively formed in the first and second positions of thebar-shaped nozzle 60. This allows the lower surface of the wafer W to befully covered with the treatment liquid without any gaps in thearrangement direction L of the ejection ports 61. The ejection of thetreatment liquid from the bar-shaped nozzle 60 in the third position iscontinued for a time period corresponding to at least one revolution(360 degrees) of the wafer W.

With the embodiment shown in FIG. 17, the treatment liquid can beejected from each ejection port 61 while changing the position of thebar-shaped nozzle 60 in the arrangement direction L of the ejectionports 61. Accordingly, even if the hole diameter of each ejection port61 is small relative to the arrangement pitch P and thus the spots S1formed on the lower surface of the wafer W by the treatment liquidconcurrently ejected from any two adjacent ejection ports 61 cannotoverlap with each other in a plan view as in FIG. 17( a), the treatmentliquid can be supplied onto the lower surface of the wafer W withoutdiscontinuity in the arrangement direction L of the ejection ports 61.Even if the treatment liquid supplied from the chemical liquid supplysource 71 a or the DIW supply source 71 b to the bar-shaped nozzle 60has a fixed pressure, the number of ejection ports 61, the hole diameterof each ejection port 61, and other parameters can be set freely whileensuring the desired jetting (ejecting) velocity of the treatmentliquid. In addition, the treatment liquid can be uniformly supplied tothe lower surface of the wafer W by shifting the bar-shaped nozzle 60during ejection. In other words, uniform liquid treatment can beperformed to the lower surface of the wafer W.

In the embodiment shown in FIGS. 17, the position of the bar-shapednozzle 60 were shifted through one third of the arrangement pitch P inthe arrangement direction L. However, not limited thereto, the positionof the bar-shaped nozzle 60 may be shifted through half (½) of thearrangement pitch P in the arrangement direction L, or one fourth (¼) ofthe arrangement pitch P in the arrangement direction L, or even finer.The amount of the shift of the bar-shaped nozzle 60 per one shiftingoperation may be set to an appropriate value in view of the arrangementpitch P of the ejection ports 61 and the size of the spots S formed onthe wafer W by the treatment liquid ejected from the ejection ports 61.

In the embodiment shown In FIG. 17, the bar-shaped nozzle 60 wasintermittently moved from the first position, to the second position,and to the third position. Alternatively, the treatment liquid may beejected from the ejection ports 61 while continuously moving thebar-shaped nozzle 50 through a predetermined distance shorter than thearrangement pitch P in the arrangement direction L. Uniform liquidtreatment can also be performed to the lower surface of the wafer W inthis way. The moving speed of the bar-shaped nozzle may be set to anappropriate value which enables the treatment liquid to be continuouslysupplied onto the lower surface of the wafer W without discontinuity inthe arrangement direction L of the ejection ports 61, in view of thesize of the spots S and the rotating speed of the wafer W.

In the embodiment shown in FIG. 17, the bar-shaped nozzle 60 movestowards the edge of the wafer W in the arrangement direction L.Alternatively, the bar-shaped nozzle 60 may be moved towards the centerof the wafer W in the arrangement direction L. Further, the bar-shapednozzle 60 may reciprocate in the arrangement direction L.

Such moving of the bar-shaped nozzle 60 may be Implemented in any waysby the horizontal moving mechanism 54. For example, the controller 100may control the horizontal moving mechanism 54 to implement the abovemoving of the bar-shaped nozzle 60. In this case, a program for movingthe bar-shaped nozzle 60 in a predefined sequence is stored within thestorage medium 106 of the controller 100.

In one embodiment, all the plurality of ejection ports 61, rather thansome of them, may be arranged in the arrangement direction L at an equalarrangement pitch P (i.e., regular intervals). The ejection ports 61arranged at the equal pitch P as such may be formed even in a regionallowing the treatment liquid to be ejected onto the central portion ofthe wafer W. Alternatively, the ejection ports 62 shown in FIGS. 10 (a),(c) may be formed in a region allowing the treatment liquid to beejected onto the central portion of the wafer W, and the arrangementpitch of the ejection port 62 may be equal to the arrangement pitch P ofthe ejection ports 61. Such configuration also enables the treatmentliquid to be supplied uniformly to the entire lower surface of the waferW.

The foregoing embodiments may be modified as follows.

In the forgoing embodiment, as shown in FIG. 14( a), the liquid-ejectingpassage 67 a and the gas-ejecting passage 67 b crossed exactly at theopening of the ejection port 61 in the bar-shaped portion 60A. However,as shown in FIG. 14( b), the gas-ejecting passage 67 b may meet theliquid-ejecting passage 67 a at a position slightly short of theopening.

In the foregoing embodiment, the DHF cleaning (chemical liquidtreatment), the DIW rinsing, the liquid droplet treatment with DIW andN₂ gas, the DIW rinsing, and the spin drying are performed in thatorder. However, the processes (treatments) performed by the substrateprocessing apparatus in the foregoing embodiment is not limited to them.For example, chemical liquid treatment (with DHF or any otherappropriate chemical liquid), DIW rinsing, and spin drying may besequentially performed. In this case, DIW rinsing may be performed byejecting only DIW without ejecting N₂ gas. The chemical liquid treatmentmay be a treatment that ejects a chemical liquid and N₂ gas at the sametime, in other words, a so-called two-fluid chemical treatment that jetsa fluid mixture of the chemical liquid and N₂ gas towards the wafer W.The gas is not limited to N₂ gas and may be any other appropriate inertgas. Further alternatively, a reactive gas may be used depending on thekind of liquid treatment.

The treatments performed by the substrate processing apparatus in theforegoing embodiment may be various kinds of liquid treatments performedto the back surface of a wafer in coating/developing processes: Forexample, the treatment may be a cleaning process after development or aremoving process for an unnecessary resist film. Alternatively, thetreatment may be a process to the lower surface (e.g., back surface) ofthe wafer to be performed as a pre-plating or post-plating process.

In the foregoing embodiment, as the substrate retaining unit of aso-called spin chuck for retaining and rotating the wafer, an assemblycomprising the lift pin plate 20 and the retaining plate integrated withthe rotary cup 36 is used. However, the bar-shaped nozzle 60 in theforegoing, embodiment may be combined with any of various types of spinchucks to construct a liquid treatment apparatus, as long as the spinchuck holds the peripheral edge of a wafer. For example, as shownschematically in FIG. 15, a mechanical spin chuck 200 configured to holdthe peripheral edge of a wafer may be combined with the treatment fluidsupply pipe 40 and the bar-shaped nozzle 60 employed in the presentembodiment. The mechanical spin chuck 200 includes a rotating member201, a plurality of (three or four) wafer retaining members 203 mountedto the rotating member 201, and a motor 202 for rotating the rotatingmember 201. The liquid treatment apparatus shown in FIG. 15 may be of atype configured to exclusively treat only the lower surface of the waferW, unlike the foregoing embodiment. In this case, a nozzle for supplyingthe treatment fluid to the upper surface is not necessary. Variousconstituent elements can be added to the configuration shown in FIG. 15(e.g., a cup for receiving splashes of the treatment fluid, a nozzle fortreating the upper surface, etc.). Incidentally, in an apparatusemploying a spin chuck as shown in FIG. 15, the distal end of thebar-shaped nozzle 60 can be extended radially outward as far aspossible, as long as it does not interfere with the wafer retainingmember 203.

In the foregoing embodiment, in the second mode, DIW guided through theliquid-ejecting passage 67 a and N₂ gas guided through the gas-ejectingpassage 67 b collide with each other at the ejection port 61 of thebar-shaped nozzle 60, whereby the DIW and the N₂ gas form a mist-likefluid mixture (two-fluid spray). In order to form such a two-fluidspray, the bar-shaped nozzle 60 may be provided, in the inside thereof,with a mixing section 69 in which the DIW and the N₂ gas collide witheach other, as shown in FIG. 18( a). The mixing section 69 is a spaceexpanding as approaching the ejection port 61. More specifically, themixing section 69 is a truncated conical space with its base (the faceof a larger area) serving as the ejection port 61, and its top face (theface of a smaller area) being positioned inside the bar-shaped nozzle60. The mixing section 69 provided inside the bar-shaped nozzle 60shapes the two-fluid spray into a desirable shape, e.g., a shape of thetwo-fluid spray spreading more isotropically. The lower surface of thewafer W can then be cleaned more uniformly.

The gas-ejecting passage 67 b that guides the N₂ gas may be configuredto extend upward in the vertical direction as shown in FIG. 18( a). Thetwo-fluid spray will thus be jetted in the vertical direction which inturn renders the two-fluid spray to collide with the lower surface ofthe wafer W in the vertical direction. Therefore, the two-fluid spraycan be collided with the lower surface of the wafer W without reducingits energy. This allows the lower surface of the wafer W to be cleanedefficiently.

In the embodiment of FIG. 18( a), the mixing section 69 and theliquid-ejecting passage 67 a are constructed in a manner that, in thefirst ejection mode, a sidewall 69 a defining the mixing section 69 doesnot deflect liquid ejected from the ejection port 61 via theliquid-ejecting passage 67 a. More specifically, as shown in FIG. 18(b), geometry parameters (e.g., angles t1 and c2, which are the angleswith respect to the vertical direction of the sidewall 69 a and theliquid-ejecting passage 67 a; the hole diameters d1 and d2 of theejection port 61 and the liquid-ejecting passage 67 a; and the positionof connection between the sidewall 69 a and the liquid-ejecting passage67 a) are determined such that a imaginarily extension of theliquid-ejecting passage 67 a towards the ejection port 61, that is, aspace 67 a′ does not contact the sidewalls 69 a. The liquid guidedthrough the liquid-ejecting passage 67 a is thus ejected obliquely fromthe ejection port 61 at the angle φ2. The angle φ2 is preferably set sothat the vector representing the direction in which the treatment liquidis ejected from the ejection port 61 has a component of the rotatingdirection R of the wafer W.

In the foregoing embodiment, the liquid treatment apparatus isconfigured such that the bar-shaped nozzle 50 can operate in two modes,one being the first ejection mode for ejecting only a liquid, the otherbeing the second ejection mode for ejecting a two-fluid spray comprisinga mixed fluid of a liquid and a gas. However, if the ejection of thetwo-fluid spray is not necessary, all the structural elements forejecting N₂ gas (e.g., the gas supply passage 40 b, the gas passageway66 b, the gas ejecting passage 67 b, 68 b, the gas supply mechanism 80,etc.) may be removed from the liquid treatment apparatus in theforegoing embodiment.

1. A liquid treatment apparatus comprising: a substrate retaining unitcomprising a retaining member configured, to hold a peripheral edge of asubstrate to retain the substrate horizontally; a rotational drivingunit configured to rotate the substrate retaining unit; a first nozzledisposed below a lower surface of the substrate retained by thesubstrate retaining unit to eject a treatment liquid towards the lowersurface of the substrate, the first nozzle comprising a plurality offirst ejection ports, which are arrayed from a position opposing acentral portion of the substrate retained by the substrate retainingunit to a position opposing a peripheral portion of the substrateretained by the substrate retaining unit; and a liquid supply mechanismthat supplies a treatment liquid to the first ejection ports, whereineach of the first ejection ports is configured to eject the treatmentliquid towards the lower surface of the substrate in an ejectingdirection which is inclined towards a rotation direction of thesubstrate rotated by the rotational driving unit.
 2. The liquidtreatment apparatus according to claim 1, wherein: the first ejectionports are arrayed along a straight line extending from the positionopposing the central portion of the substrate retained by the substrateretaining unit to the position opposing the peripheral portion of thesubstrate retained by the substrate retaining unit, and the straightline extends in a radial direction of the substrate held by thesubstrate retaining unit or extends parallel to the radial direction. 3.The liquid treatment apparatus according to claim 1, wherein: the firstnozzle comprises a bar-shaped portion extending in a radial direction ofthe substrate retained by the substrate retaining unit, and the firstejection ports are provided in the bar-shaped portion.
 4. The liquidtreatment apparatus according to claim 1, wherein: the first nozzlecomprises at least one second ejection port provided in an area radiallyinside an area in which the first ejection ports are provided, and thesecond ejection port is configured to eject a treatment liquidvertically upward.
 5. The liquid treatment apparatus according to claim1, wherein: at least radially outermost one of the plurality of thefirst ejection ports is configured to eject a treatment liquid in anejecting direction having a radially outward component.
 6. The liquidtreatment apparatus according to claim 1, wherein: assuming that an areacovered by a treatment liquid at a moment when the treatment liquidejected from an ejection port of the first nozzle reaches the lowersurface of the substrate retained by the substrate retaining unit isreferred to as a “spot”, the first ejection ports are configured to formspots adjacent two of which overlap with each other.
 7. The liquidtreatment apparatus according to claim 1, wherein: the first nozzlecomprises at least one second ejection port provided in an area radiallyinside an area in which the first ejection ports are provided, and thesecond ejection port is configured to discharge a treatment liquidvertically upward; and assuming that an area covered by a treatmentliquid at a moment when the treatment liquid discharged from an ejectionport of the first nozzle reaches the lower surface of the substrateretained by the substrate retaining unit is referred to as a “spot”, anradially innermost one of the plurality of first ejection ports isconfigured to form a spot which overlaps with a spot formed by atreatment liquid ejected from the second ejection port.
 8. The liquidtreatment apparatus according to claim 1, further comprising a second,nozzle configured to supply a treatment liquid onto an upper surface ofthe substrate retained by the substrate retaining unit.
 9. The liquidtreatment apparatus according to claim 1, wherein: the liquid supplymechanism comprises a variable throttle, and wherein said liquidtreatment apparatus further comprises a controller configured to vary anopening of the variable throttle according to a predetermined sequence,when the treatment liquid is being supplied from the first ejectionports onto the lower surface of the substrate.
 10. The liquid treatmentapparatus according to claim 1, wherein: the first nozzle comprises abar-shaped portion extending in a radial direction of the substrateretained by the substrate retaining unit, and a central portion locatedat a position opposing a central portion of the substrate retained bythe substrate retaining unit; the first ejection ports are provided inthe bar-shaped portion; the central portion comprises at least onesecond ejection port configured to eject a treatment liquid verticallyupward; a through-hole is formed in the central portion of the substrateretaining unit, and a treatment liquid supply pipe penetrates throughthe through-hole; a cover is provided at the central portion of thefirst nozzle to prevent a treatment liquid once ejected towards thesubstrate from flowing into the through-hole; the first ejection portsand the at least one second ejection port are arrayed on a straightline, in a plan view.
 11. The liquid treatment apparatus according toclaim 1, wherein: the first nozzle comprises a bar-shaped portionextending in a radial direction of the substrate retained by thesubstrate retaining unit, and a central portion located at a positionopposing a central portion of the substrate retained by the substrateretaining unit; the first ejection ports are provided in the bar-shapedportion; the central portion comprises at least one second ejection portconfigured to eject a treatment liquid vertically upward; a through-holeis formed in the central portion of the substrate retaining unit, and atreatment liquid supply pipe penetrates through the through-hole; acover is provided at the central portion of the first nozzle to preventa treatment liquid once ejected towards the substrate from flowing intothe through-hole; assuming that an area covered by a treatment liquid ata moment when the treatment liquid ejected from an ejection port of thefirst nozzle reaches the lower surface of the substrate retained by thesubstrate retaining unit is referred to as a “spot”, the first ejectionports and the at least one second ejection port are configured to formspots arrayed along a straight line, in a plan view.
 12. The liquidtreatment apparatus according to claim 1, wherein: the first nozzlecomprises a bar-shaped portion extending in a radial direction of thesubstrate retained by the substrate retaining unit, and a centralportion located at a position opposing a central portion of thesubstrate retained by the substrate retaining unit; the first ejectionports are provided in the bar-shaped portion; the central portioncomprises at least one second ejection port configured to eject atreatment liquid vertically upward; a through-hole is formed in thecentral portion of the substrate retaining unit, and a treatment liquidsupply pipe penetrates through the through-hole; a cover is provided atthe central portion of the first nozzle to prevent a treatment liquidonce ejected towards the substrate from flowing into the through-hole;assuming that an area covered by a treatment liquid at a moment when thetreatment liquid ejected from an ejection port of the first nozzlereaches the lower surface of the substrate held by the substrateretaining unit is referred to as a “spot”, the first ejection ports andthe at least one second ejection port are configured to form spotsarranged on a polygonal line, in a plan view.
 13. The liquid treatmentapparatus according to claim 1, wherein: the first ejection ports arearrayed along a straight line extending from the position opposing thecentral portion of the substrate retained by the substrate retainingunit to the position opposing the peripheral portion of the substrateretained by the substrate retaining unit; said liquid treatmentapparatus further comprises; a horizontal moving mechanism configured tomove the first nozzle along the straight line along which the firstejection ports are arrayed; and a controller configured to control thehorizontal moving mechanism to move the first nozzle according to apredetermined sequence, when the first ejection ports eject a treatmentliquid towards the lower surface of the substrate.
 14. The liquidtreatment apparatus according to claim 13, wherein: at least some of theplurality of first ejection ports are arrayed along the straight line atregular intervals; and the controller is configured to control thehorizontal moving mechanism to move the first nozzle at a distance lessthan the interval between adjacent two of said at least some firstejection ports.
 15. A liquid processing method comprising: retaining asubstrate in a horizontal posture; providing a first nozzle comprising aplurality of first ejection ports below a lower surface of the substrateretained by the substrate retaining unit such that the first ejectionports are arrayed from a position opposing a central portion of thesubstrate to a position opposing a peripheral portion of the substrate;rotating the substrate; and ejecting a treatment liquid from the firstejection ports toward a lower surface of the substrate in ejectingdirections each having a component in a rotation direction of thesubstrate.